Sn=n/2 (2a1 +(n-1)d)
[s5= 5/2 (2a1 +(5-1)d) = 5a1+10d]
s6=3(2a1+5d) = 6a1+15d
s4=2(2a1+3d) = 4a1+6d
6a1+15d -(4a1+6d) = 5 -----(1)
s7=7/2(2a1+6d) =7a1+21d
6a1+15d + 7a1+21d = 21 -----(2)
(1) 2a1+9d=5 -----(3)
(2) 13a1+36d=21 ----(4)
(3)*4 ; 8a1+36d=20 ----(5)
(4)-(5) 5a1 = 1
so a1 = 1/5
(3) 2a1+9d=5
2(1/5)+9d = 5
9d = 5-2/5 =23/5
d = 23/45
so [s5= 5/2 (2a1 +(5-1)d) = 5a1+10d = 5(1/5) + 10(23/45) = 1 + 5.11 = 6.11 ]
i'm not sure about the answer but the process is correct
Answer:
35
Step-by-step explanation:
Answer:
2:5
Step-by-step explanation:
c : a : a²
8 5 7
add 8 + 5 + 7 = 20
comedies = 8
8:20 | factors of 8 and 20 are 4
8 / 4 = 2
20 / 4 = 5
new ratio; 2:5
Answer:
6
Step-by-step explanation:
